Use the socket option constants defined in the golang.org/x/sys/unix
package instead of duplicating them in this package.
Note that for now, sysIP_RECVDSTADDR, sysIP_RECVIF and sysIP_RECVTTL
still need to be defined because they are used in code shared with other
platforms.
Change-Id: I2b3b8621108c9399f1d36bab97c65fd349fa0839
Reviewed-on: https://go-review.googlesource.com/c/net/+/304712
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>